1. Field of the Invention
The present invention relates to a metering device and a circumferential seal for the clearance space or gap between a vacuum pressure chamber formed by a trough-shaped casing and a revolving transporting disk for sealing the vacuum pressure chamber, and preferably, for a single-grain sowing machine.
2. The Prior Art
German utility model G 85 05 231.0 discloses a sowing unit for single-grain sowing machines. This unit has a vacuum pressure chamber of known construction. In this connection, a transporting disk serves for receiving and transporting individual seed grains from a supply source to the planting site where it is deposited. The vacuum that is applied cooperates with this transporting disk.
This prior art device has these disadvantages. The outer part of the transporting disk faces the vacuum pressure chamber, and the disk is slightly conical in shape for this purpose. The disk is pressed onto an annular circumferential seal made of felt mixed with graphite with the seal being arranged in the casing of the vacuum pressure chamber. This causes considerable friction to occur, which leads to the undesirable heating of the transporting disk and to rapid wear of the circumferential seal.